I find geoemtry very hard, and I find proof very hard, causing me to check if my work is correct or not. I am also doing this problem with you guys right now. Please help along the way as well
If it is given that two triangles are similar, then it also means that the sides are proportional. Does this detail help you make progress here?
I have already figured it out, thank you though. I will show you my thought process in a second after I finish one step of this problem
Δ ABC ~ Δ ACD
AB /AC = AC/ AD
AB / 6 = 6 / 3 multiply both sides by 6
AB = 36 / 3 = 12